This description relates to absolute time recovery in wireless networks.
Cellular wireless communications systems are designed to serve many access terminals distributed in a large geographic area by dividing the area into cells, as shown in FIG. 1. At or near the center of each cell 102, 104, 106 (generally 102), a radio network access point, also referred to as a macro base transceiver station 108, 110, 112 (generally 108), is located to serve access terminals 114, 116 (generally 114) (e.g., cellular telephones, laptops, PDAs). Each cell 102 is often further divided into sectors 102a-c, 104a-c, 106a-c (generally 102a) by using multiple sectorized antennas. A base transceiver station 108 corresponding to a cell 102 serves one or more sectors 102a and communicates with multiple access terminals 114 within the cell 102.
Occasionally, macro signals in the environments of the access terminals 114, which normally provide timing information, are weak. For this reason, it is difficult to decode, for example, sync messages, included in the macro signals. Accordingly, it is desirable to recover absolute time from the timing pattern of weak macro signals provided by a local base transceiver station 108.
The 1x EV-DO protocol has been standardized by the Telecommunication Industry Association (TIA) as TIA/EIA/IS-856, “CDMA2000 High Rate Packet Data Air Interface Specification,” 3GPP2 C.S0024-0, Version 4.0, Oct. 25, 2002, which is incorporated herein by reference. Revision A to this specification has been published as TIA/EIA/IS-856A, “CDMA2000 High Rate Packet Data Air Interface Specification,” 3GPP2 C.S0024-A, Version 2.0, July 2005. Revision A is also incorporated herein by reference. Revision B to this specification has been published as TIA/EIA/IS-856-B, 3GPP2 C.S0024-B and is also incorporated herein by reference. Other wireless communication protocols can also be used.